Publication and Communication

The influence of Greenland ice sheet melting on the Atlantic meridional overturning circulation during past and future warm periods: a model study

Authors

Blaschek, M., Bakker, P., & Renssen, H.

First Authors affiliation

VU Amsterdam

Journal

Climate Dynamics

Abstract

The sensitivity of the climate system to changes in radiative forcing is
crucial for our understanding of past and future climates. Especially
important are feedbacks related to melting of ice sheets like the
Greenland ice sheet (GIS) and its potential impact on the Atlantic
meridional overturning circulation (AMOC). These effects are likely to
delay and dampen predicted long-term warming trends. Estimates of
climate sensitivity may be deduced from palaeoclimate-reconstructions,
but this raises the question whether past climate sensitivity is
applicable to the future. Therefore we have analysed the impact of GIS
melt water on the AMOC strength in two past warm climates (last
interglacial and early present interglacial) and three future scenarios
with three different model parameter sets. These model parameter sets
represent three different model sensitivities to freshwater
perturbation: low, moderate and high. In both the moderate and high
sensitivity versions, we find for lower GIS melt rates (below 54 mSv,
Sv = 106 m3/s)
a clear difference between past and future warm climates in the
sensitivity of the AMOC to GIS melt. This difference is connected to the
convective activity in the Labrador Sea and the amount of additional
surface freshening due to sea ice melting. In contrast, for higher GIS
melt rates (over 54 mSv) we find similar reductions of the AMOC strength
in all cases. Considering the low sensitivity version of our model, we
find that for all GIS melt rates the influence of freshwater forcing on
the AMOC is independent of the background climate. Our results and
implications are thus strongly determined by the parameter set
considered in our model. Nonetheless, our results from two out of three
model versions suggest that proxy-based reconstructions of past AMOC
sensitivity to GIS melt are likely to be misleading if interpreted for
future applications.